That young-adult fantasy was published by Longmans in Canada and Harcourt Brace in America with illustrations by Trina Schart Hyman, when Nichols was 20 or 21.
Having experienced success early in life as a writer of adolescent fantasy, Nichols' moved to adult historical fiction.
After divorcing in 1998, health problems forced Nichols to live in a chronic care facility in Toronto.
Predating Harry Potter by decades, her beautifully written books feature characters with unusual powers, wizards and worlds of wonder where good struggles with evil.
Nichols received the Government of India Prize in 1962 for a 100-page biography of Catherine de' Medici.